The remains of dud Martian probe Phobos-Grunt will fall to Earth next month, the Russian space agency announced.
Roscosmos said that the exact time or place couldn't be forecast until a few days before it falls, but "according to expert estimations", it would hit the ground sometime between January 6 and January 19.
"Between 20 …

To guarantee catching all 30 bits in a portable way...

NASA nothing to write home about

"According to Popovkin, Mars is a planet that "doesn't like Earthlings". He claims that only 30 per cent of Soviet-Russian launches to the planet were successful, although NASA alleges that all 17 of Russia's attempts have failed."

NASA's own record is only around 50% and the Ruski's did manage to land on Venus - more that NASA ever did...

Depends on how do you count failures

Russians landed _FIRST_ on mars - 1971. However not a single one of the scientific experiments on board of Mars 1 and Mars 2 worked. The orbiter components worked in both. Ditto for Mars 3-6 launched in the 70-es: all returned some data but lander components did not manage to complete all of their program.

NASA numbers are correct at some level - not a single Russian mission managed to fulfill its complete scientific programme. However out of 17 around 6 managed to return something useful and most importantly new from a scientific perspective - f.e. the discovery of some level of ionosphere, etc.

After understanding what's on Venus, it could be of little scientific interest landing there, especially since a lander MTBF could be measured in seconds due to the heat and aggressive atmosphere. That's why recent missions are more focused to understand why Venus evolved that way, such missions need planetary-scale data, not a few local ones.

Anyway NASA sent probes to every planet in the Solar System. Managed to reach Mercury twice, which is the one of the most complex mission to achieve. It was able to land on Mars several times, send a probe inside Jupiter atmosphere, and land another on Titan. The New Horizon is on its trip to Pluto. The Voyagers are still transmitting data after all these years, and are reaching the outer limit of the solar system, past the heliopause. Russian were only able to send probes to the two nearest planets, lacking the upper stages able to send a probe to an outer planet and the "deep space" network to manage it. Maybe they could manage it using a lot of gravity-assists, but that requires great planning and mission control. In the past forty years, space exploration was mostly "made in NASA" (but some good European missions).

Once again

Hang on .... They (Nasa et.al) are reputedly capably of tracking objects as small as my earing so they don't small into the now defuct shuttle, yet they can't tell where or when a 200Kg lump of rather warm and probably slightly damaged bit if metal travelling at sill speeds is going to land?

Depends in many things

It's very hard to narrow it down further. Rather than a simple orbit in a vacuum, the probe is now interacting with the Earth's atmosphere. The time of the actual re-entry will be governed by the attitude of the probe with respect to the atmosphere as that will affect the amount of drag it experiences. The other big factor is how active the Sun will be, the more active the Sun, the more it heats the atmosphere which expands and causes more drag. Skylab was the most famous victim of atmospheric heating.

A debris in outer space follows a trajectory that is only due to its mass and speed (there are some other effects like radiation pressure and so on, but if the debris is small enough they could be irrelevant). When it start to hit the atmosphere, aereodinamycs effects become important. Then the shape, the orientation, type of material are key factors, together the atmospheric ones (density, winds speeds, etc.)

The problem is when the probe breaks apart, there is no way to understand exactly how it happens and what fragments are produced and which final trajectory they take (a fuel explosion can send them in very different directions, for example), especially if the probe is out of control and probably lost attitude control. If you wish to setup a cluster of ZX Spectrums to calculate it, start to gather a lot of them...

271.74 days, more precisely ...

90% decays in 902.70 days, 90% of what's left in the next 902.70 days, etc. So 1% of it will still be present in 5 years, but it is 10 µg = 1.1*10^17 atoms to start with, to be spread out over a large debris field (thousands of hectares), probably not to worry.

Why the landing is so variable

AFAIK the primary force in dragging the Grunt down is the ever-varying ultra-high atmosphere of the Earth. Since atmospheric friction is quite variable at those levels, NASA won't be able to predict reentry until atmospheric contact is either very intense or at least continual. The probe will 'skip' off the highest levels several times before it actually dives-down.

Excellent

Well we're at 52 degrees north so I'll be out in the garden watching for it if it's going to be bright enough to get through London's light pollution or else I'll take a week off and bugger off somewhere darker and take a quality pair of binos.

Oh no, I won't buy a ticket.

I'd best not buy a lottery ticket on the day when the failed craft plunges to the earth's surface. Knowing my luck I'll be holding the jackpot winning ticket in my hand just as a chunk of the satellite takes me out.

Translation fail?

Since 100km is pretty generally regarded as the edge of space I doubt the accuracy of the statement about the fuel burning up in "the dense atmosphere of the Earth at an altitude of approximately 100km".